1. Field of Invention
The present invention relates generally to a low thread force cable tie, and more particularly to a relief structure that allows for reduced resistance to threading for a cable tie with a metal locking device.
2. Description of Related Art
Plastic cable ties having metal locking device inserts are well known in the art. Examples of such include U.S. Pat. No. 3,457,598 to Mariani and U.S. Pat. No. 5,517,727 to Bernard et al.
Cable ties of this type include a metal locking device partially embedded at an angle within a strap accepting channel of a cable tie head. The metal locking device is situated at an angle that allows insertion of a cable tie strap in an insertion direction, but allows for engagement of the locking device with the strap when it is pulled in a removing direction to prevent removal. The metal locking device of such conventional cable ties is in the form of a cantilevered beam that is fixed at one end and extends into the strap accepting channel at the free end.
Resistance to insertion in such cable ties is limited by the flexibility of the metal locking devices. Most conventional cable ties have a solid support section in the region of the fixed end of the metal locking device. Prior attempts to reduce insertion force have resulted in use of thinner metal locking devices, which while reducing insertion force have the undesirable affect of reducing the locking force of the cable tie. As such, these are usually undesirable.
One prior attempt at reducing insertion force while retaining loop tensile strength can be found in U.S. Pat. No. 5,517,727 to Bernard et al. In this cable tie, a cored out pocket is provided on the external surface of the locking head adjacent the fixed end. This allows for a slight rotation of the fixed end of the metal locking device during insertion of the strap, which lowers insertion force by reducing resistance to rotation. However, the pocket is only taught to be made external.
There is a need for an improved locking device that can provide better resistance to removal while achieving a low insertion force.
There also is a need for a low insertion force cable tie having a clean, aesthetic exterior appearance.
It is an object of the invention to provide a cable tie utilizing a metal locking device that has improved retention strength and a low insertion force.
The above and other objects are achieved by a cable tie comprising a strap including a first end and a free end, a locking head secured to the first end of the strap, and a metal locking device. The locking head including an end wall, an inner wall and side walls that define a strap accepting channel in the head. The strap accepting channel has a strap entry end and a strap exit end. The locking head further includes a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head. The metal locking device is mounted within the metal locking device receiving cavity by having a fixed end mounted to the end wall of the locking head and a free end positioned within the strap accepting channel. The locking head includes a recessed pocket provided between the fixed end of the metal locking device and the strap accepting channel that opens to the metal locking device receiving cavity. The recessed pocket defines a thinned support membrane immediately adjacent the fixed end of the metal locking device that allows for slight rotation of the fixed end toward the strap accepting channel when feeding the strap through the strap accepting channel, which reduces strap insertion force.
The invention also provides a method of making a cable tie comprising the steps of: molding a cable tie with a first end and a free end and a locking head secured to the first end of the strap, the locking head including an end wall, an inner wall and side walls that define a strap accepting channel in the head, the strap accepting channel having a strap entry end and a strap exit end, the locking head further including a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head that includes a recessed pocket; and inserting a metal locking device into the metal locking device receiving cavity and mounting one end of the locking device into the end wall of the locking head closely adjacent to the recessed pocket such that the recessed pocket is situated between the metal locking device and the strap accepting channel and a support membrane of a predetermined thickness is formed between the locking device and the recessed pocket, a free end of the metal locking device being positioned within the strap accepting channel.